Magnetic nanoparticles are widly used in the field of nucleic acid purification. All commercially available large scale magnetic nanoparticles have superparamagnetic properties. In contrast, ferrimagnetic nanoparticles are not commercially available and only known from academic publications. Such publications include nanoparticles with silica coatings (Chen et al; J. of alloys and compounds 497 (2010) 221-227; Wang et al; Bioresource Technology 101 (2010) 8931-8935; Reza et al; Cent. Eu. J. Chem 5 (2010) 1041-1048). One of the major drawbacks of the majority of preparations of ferrimagnetic nanoparticles known in the art where low pressure reactors at <100° C. are used is that the synthesis is difficult to upscale and automate (Wang et al; Bioresource Technology 101 (2010) 8931-8935; Reza et al; Cent. Eu. J. Chem 5 (2010) 1041-1048).
The use of glycols as solvent and reducing agent for the synthesis of ferrimagnetic nanoparticles has been shown (Wiley et al; Nano Lett. 4 (2004) 1733-1739; D. Larcher, R. J. Partrice; J. Solid State Chem. 154 (2000) 405-411; Gai et al; J. Phys. D: Appl. Phys. 43 (2010) 445-553)—also in combination with the surfactant—free synthesis route (“Green synthesis route”) (Liu et al; Eur. J. Inorg. Chem. 2 (2010) 4499-4505). These preparations are focused on the use of iron(III) salts which result in poor size distribution and yield when upscaled to more than 100 mL scale.
Silanization of ferrimagnetic nanoparticles is only known in the art according to the Stöber method which relies on harmful alkoxy silanes. Using harmless SiO2 solution in purely aqueous conditions have only been shown in the context of superparamagnetic particles (Philipse et al; Langmuir 10 (1994) 92-99).
Extraction of nucleic acids by means of hydrothermally prepared ferrimagnetic particle structures are described (Gai et al; J. Phys. D: Appl. Phys. 43 (2010) 445-553). These publications used ferrimagnetic particles which were produced by silane chemistry or without silicone containing coating, wherein the production was complex or resulted in a poor eluation.
The object of the present invention is the provision of monodisperse silanized ferrimagnetic iron oxide particles for nucleic acid binding which do not show the above mentioned drawbacks and a method for producing the same.